A high brightness centralized lighting system has been proposed for various lighting applications where it is desired to have a central light source and a plurality of remote locations which are illuminated from the central light source over optical fibers or light pipes. An example of such a centralized lighting system can be found in U.S. Pat. No. 4,958,263 issued to Davenport et al on Sep. 18, 1990 and assigned to the same assignee as the present invention. In this patent, a light source is provided having a central ellipsoidally-shaped arc tube and a number of extending tube shaped extensions formed thereon. Each of the extending tube portions is coupled over optical fibers to various locations around a vehicle for providing lighting needed for forward illumination, tail lighting and overhead lighting for instance. It has been found with such an arrangement that there is little uniformity of the light output for the various tubular extensions. Additionally, it has been found that in order to provide the necessary amount of illumination at the desired location, large diameter optical fibers on the order of approximately 10 mm or greater are required. For such a large optical fiber, in addition to being more expensive, it is difficult to maneuver and turn the optical fiber for placement within the body of the vehicle. Another example of the use of a centralized lighting source and optical fibers for providing the forward illumination in a vehicle, can be found in U.S. Pat. No. 5,278,731 issued to Davenport et al. on Jan. 11, 1994 and assigned to the same assignee as the present invention. In this patent, a single optical fiber is introduced to a substantially conventional automotive reflector assembly except that a V-shaped mirror provides for distribution of the light output from the end of the fiber to the reflector surface for transmission through a lens member. In the configuration of this patent, assuming that the optical fiber is 10 mm in diameter, the beam produced would have approximately a 5 degree vertical spread. The 5 degree vertical spread exceeds the 4 degree right, 4 degree down SAE test point and further exhibits excessive foreground illumination. It would therefore be desirable to provide a centralized lighting system for automotive applications that would allow for the use of smaller diameter optical fibers and would achieve the appropriate beam pattern in terms of spread characteristics.
A further problem to be solved in providing a centralized lighting system for use in automotive applications involves the ability to provide a light output that is uniform in appearance from both the left and right side of the vehicle. An example of a centralized lighting system that provides a substantially uniform appearing light output at both sides of a vehicle can be found in U.S. Pat. No. 5,222,793 issued to Davenport et al on Jun. 29, 1993 and assigned to the same assignee as the present invention. In this patent, in order to achieve a multiple beam output from a single light source, a split reflector configuration is utilized to provide two light outputs and optical fibers are disposed in contacting side by side relation for a specific length and then split for distribution to the two sides of the vehicle. Although effective in achieving a multiple beam output from a single light source, the system of patent No. 5,222,793 requires precision machining operations to manufacture the split reflector arrangement and as well, because the optical fibers are in a contacting relation to one another, insulating problems between the contacting optical fibers can sometimes be experienced.
Still a further problem to be dealt with in providing multiple light outputs from a single centralized light source is that of achieving an optimum packing fraction between the multiple optical fibers that are being utilized. In other words, by directing light from a single light source into a plurality of input surfaces of optical fibers bundled together, there will be spaces formed between the optical fibers that will result in light which is presented thereto being lost. The amount of surface area associated with the optical fiber inputs divided by the area of the light output presented to the optical fibers is defined as the packing fraction and it is desirable to have this value maximized. In fact, it would be further desirable to provide a light output from the light source that was divided into individual light spots prior to delivery to the input surface of the optical fiber and to provide such individual light spots in a cost effective manner without requiring the use of complicated reflector devices that are manufactured only to tight tolerances.